High HC

[rlux4]

Instead of doing it the hard way (study) I'm coming to you all for the collective wisdom of Fiaters.
I just passed my bi-annual smog check. However, the hydro-carbons reading was kind of high. 152 ppm is the upper acceptable limit, and mine read 112.
Here's the question: What causes the high HC reading? 2nd part: is the NO related? It also read on the high side.
This is an easy one for your Mark.
Ron

[htchevyii]

Hey Ron, I found this:
http://www.aircare.ca/repinfo-ere-causes-hc.php

When I had my Dad's MGB smogged he said it was the highest HC he had ever seen. I didn't know it was possible, but it was actually caused by running super lean. It was so lean it was missing and pumping the fuel thru the exhaust.

[So Cal Mark]

to make an educated response, I need to see the CO, HC and NOx numbers. With the scant info you posted I'd say your catalyst is losing efficiency

[majicwrench]

HC is unburned fuel. Either a cylinder missing, or too rich. Converter can deal with some of it, but it is probably mixture related, esp since the numbers not really that high. Is this is carbed or fuelie car?? Thank gosh I don't have to deal with emmisions testing!
Keith

[So Cal Mark]

112ppm is not high HC for a 1980s car. In fact, that number would have been well within limits a few years ago and is well below what the car was originally designed to meet. Calif keeps tightening standards each year, making it tougher and tougher to get the carbed cars through the test. As for emission testing, it's very enlightening to look at the emission numbers to assess engine condition and state of tune. BTW, an ignition misfire at idle would result in HC levels of about 1500-2000 ppm

[rlux4]

Thanks guys. That's good to know Mark. Keith, it's an 82, fuelie all the way! Here is the sheet of the results:


(Thumbnail so it would be readable)

I replaced the cat last year and the car starts on first click. It idles beautifully, and runs like a champ. The guy at the smog shop just mentioned that he thought the HC was kind of high. What burns me up is why I had to go to a Test Only shop: the reason given is HEP (high emitter profile). I'm being profiled! The numbers when I got my car (last time it was smogged) came out terrific, so just because it's an "older" car, I have to go through "enhanced" smog check. I don't want to live here anymore.
I thought maybe these numbers were because the ignition timing was a little off. I set it to 10° btdc, and then tweaked it to the point where it idled and started the best. Couple of degrees, maybe.
Ron

[So Cal Mark]

advancing the timing will raise HC. The State of Calif compiles results, so apparently 82 Spiders are fouling the air quality more than other years and require more stringent testing

[rlux4]

I guess I left myself open for that one!
Ron

[mdrburchette]

Shoulda got a 72. They run so clean CA doesn't see a need to test them any more.

[rlux4]

Et tu Denise?
Ron